The present invention belongs to the field of eye drops and is based on the discovery that an addition of aliphatic dicarboxylic acids to eye drops is able to extend the period of dwell of the drops on the surface of the eye. The addition of dicarboxylic acids having 8 to 11 carbon atoms according to the general formula (CH.sub.2).sub.6-9.(COOH).sub.2 has been found to be particularly suitable; these are suberic acid, azelaic acid, sebacic acid and nonane dicarboxylic acid. From these dicarboxylic acids, which are advisably employed in the form of their sodium or calcium salts, sebacic acid has been found to be most suitable. In the form of an oily film, it offers protection against too rapid evaporation of the lacrimal fluid on the eye. The addition according to the invention of, for example, sebacic acid to conventional eye drops thus retards the evaporation of the dropped-in liquid and increases the oil layer disposed on the surface which is anchored in the aqueous partial layer of the lacrimal film by way of the hydrophilic groups in the dicarboxylic acid.
The object of the present invention is thus the use of dicarboxylic acids having 8 to 11 carbon atoms as an additive in the production of eye drops. The dicarboxylic acids may advisably be employed in the form of their sodium or calcium salts; the use of sebacic acid, particularly in the form of its sodium or calcium salt, has been found to be most advantageous.
Literature is known which discloses the use of dicarboxylic acids, particularly dicarboxylic acids having 7 to 13 carbon atoms, for the treatment of various skin diseases. According to WO-A1-88/00465, these dicarboxylic acids are employed, for example, as topical treatments for rosacea. EP-A2,229,654 relates to the treatment of inflammatory dermatoses, infectious cutaneous diseases and loss of hair as a result of inflammations or hormonal anomalies. U.S. Pat. 4,292,326 employs dicarboxylic acids having 7 to 13 carbon atoms for the treatment of acne, hyperpigmentary dermatoses as well as hyperpigmentations of the skin. Finally, according to U.S. Patent 4,034,077, sebacic acid is employed in concentrations from 2 to 30% as an additive in baby ointments and baby powder to protect against skin irritations when wearing diapers.
These proposed uses of dicarboxylic acids disclosed in the literature, particularly those containing 7 to 13 carbon atoms, relate exclusively to the treatment of skin diseases and thus do not constitute anticipation of the subject matter of the invention.